Optimization of thickness and uniformity of photonic structures fabricated by interference lithography
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We study the influence of the absorption of materials used for holographic fabrication of photonic structures on their uniformity along the film thickness. We demonstrate theoretically and experimentally a strong dependence of structure thickness and uniformity on the exposure dose of the interference pattern. A novel technique is proposed to overcome the absorption effect and to fabricate thick two- and three-dimensional structures, which are uniform throughout the film thickness. It consists of exposing once again the sample by an additional and independent counterpropagating uniform beam, which allows to compensate the diminution of the light intensity of interference pattern. These results are very useful for the fabrication of high quality polymer-based photonic crystals.
KeywordsPhotonic Crystal Interference Pattern Photonic Structure Uniform Beam Structure Thickness
We are grateful to J. Lautru for his invaluable help and access to the clean room and to the use of scanning electronic microscope. This work was partially supported by Institute d’Alembert of the Ecole Normale Supérieure de Cachan and by the “Triangle de la Physique”, in the framework of the project “PUTTON”. Nguyen Thi Thanh Ngan acknowledges the fellowship from the Vietnam International Education Development “322 program” and the support from USTH university.